The present invention relates to roll and roll-driving assemblies.
In particular, the present invention relates to that type of roll structure where an internal shaft is surrounded by a rotary shell while a drive is transmitted to the rotary shell from an input shaft which is coaxial therewith. Thus, through a suitable gear transmission a drive from the input shaft is transmitted to the shell so as to rotate the latter with respect to the stationary shaft. Several different types of drives of the above general type are known. Thus, according to one known structure there is a three-ring bearing including a pair of spherical roller bearings with a ring disposed therebetween and utilized to conduct the rotation to the shell by way of rigid connections from a shaft to the shell. Angular displacements between the axis of the roll assembly and the shell are compensated at the spherical bearing structure. The disadvantage of this type of construction resides in the fact that it has a large radial space requirement which inhibits the possibility of utilizing a three-ring bearing which is of a sufficient size. Thus with this type of construction it is essential to utilize a bearing which is too small, with the result that the bearing has only a short operating life.
A further type of known drive utilizing a three-ring bearing arrangement has been provided with one cylindrical and one spherical roller bearing, the ring between them being utilized to conduct the rotary motion to the shell by way of a double-tooth coupling from an input shaft. This double-tooth coupling has curved teeth which permit a slight angular displacement between the central axis of the roll and the housing of the bearing. However, this known drive suffers from the same drawback as the above-referred to known construction, namely, the impossibility of using a large enough bearing structure because of the space requirements.
It has also been proposed to provide on at least one of a pair of opposed side shafts which are parallel to the drive shaft a pair of traction wheels one of which meshes with the driving gear on the drive shaft while the other meshes with an extremely toothed ring. When the drive shaft of this construction is rigidly mounted in bearings, the above side shaft is disposed obliquely with respect to the axis of a flange of the structure in such a way that when a predetermined radial load is applied to the shell the flange axis and the side shaft axis will become parallel to each other. With this type of construction it is possible to transmit the power only along one path from the input shaft to the rotary shell. Such a construction has a single-pivot bearing structure so that of necessity there will be an uneven, rough operation if the shell is displaced with respect to the drive. In addition, the gear which drives the shell can only accept limited loads because the teeth of this gear are always urged to one side. Moreover, since the entire driving structure is situated outside of the roll, there are large space requirements.
A second possible alternative with this type of construction resides in transmitting the power along two paths from the input shaft to the shell, with this construction being based upon a two-pivot support and a symmetrical load application. However, this construction suffers from the drawback that equal distribution of the loads among both of the power transfer paths cannot be reliably achieved because of unavoidable inaccuracies in the manufacturing of the components utilized in the transmission.
According to a third possible alternative of the above type of construction the power is transmitted along three paths from the input shaft to the shell. However, this construction also is based upon a two-pivot supporting arrangement with the supporting of the gear which drives the shell being deficient in the same way as in the above two alternatives. Furthermore, equal distribution of power among the three power transfer paths cannot be reliably achieved because of the inaccuracies in the manufacture of the transmission components. A further drawback of such a construction resides in the fact that the oblique position of the side shaft is preliminarily determined to achieve a parallel relationship only when a certain load is applied, so that a serious restriction is placed on the possibility of varying the load, or in other words the line-pressure loading of the shell.